DEFORMATION OF ROCKS 



185 



in some of them the cleavage is also monoclinal, but still shows 

 divergence or convergence downward upon opposite sides of a 

 fold according to the law. In the monoclinal svncline the 

 monoclinal cleavage on opposite sides of the limb converges 

 downward, and in the monoclinal anticline the monoclinal cleav- 

 age on opposite sides of the limbs diverges downward. 



Fig. 3. 



It may be suggested that in cases where metamorphism has 

 gone so far that it is difificult to determine bedding this prin- 

 ciple of the convergence downward of cleavage on opposite 

 sides of a syncline, and divergence downward of cleavage on 

 opposite sides of an anticline, ma)- be used to determine whether 

 a series of folded exposures are anticlinal or synclinal. In 

 another case, where the bedding is somewhat obscure and dips 

 difficult to get, it may be used as confirmatory evidence of the 

 observations made upon the bedding. 



Relations of cleavage produced by shearing to shortening. — In 

 the production of cleavage as a result of simple shearing, 

 Professor Hoskins has pointed out that the cleavage approaches 

 parallelism to bedding faster than does a line originally normal 

 to the bedding.' As the actual positions of the cleavage result- 

 ing from definite shears and the relations of original circles to 

 equivalent flattened ellipses (Fig. 3) are matters of some practical 

 importance in the field, Mr. E. C. Bebb was asked to tabulate the 

 positions of the major axes of the flattened ellipses, the values of 



' Flow and Fracture of Rocks as Related to Structure, by L. M. Hoskins. 

 Appendix to Principles of North American pre-Cambrian Geology, by C. R. Van 

 HiSE, Sixteenth Ann. Rept. U. S. Geol. Surv., Part I, 1896, pp. 870-S71. 



